1. Field of the Invention
The present invention relates to a process for producing hydroquinone having a good color from p-diisopropylbenzene dihydroperoxide (usually referred to hereinafter as "p-DHP") at a high yield.
2. Description of the Prior Art
It has been previously known in the art that hydroquinone is produced by oxidizing, in a liquid phase, p-diisopropylbenzene (usually referred to hereinafter as "p-DIPH") and/or p-diisopropylbenzene monohydroxyperoxide (usually referred to hereinafter as "p-MHP") with molecular oxygen from p-DHP, followed by decomposition of p-DHP in the presence of an acid catalyst. However, in such an oxidation reaction, it is difficult to selectively produce only p-DHP. Furthermore, the separation of high purity p-DHP from the oxidation reaction mixture is a difficult operation and is complicated, hence expensive, to operate. For these reasons, materials other than p-DHP--including various kinds of by-products, unreacted starting materials, intermediate products and the like--are generally used as starting materials for the acid decomposition. However, when these starting materials are decomposed in the presence of an acid, it is not easy to isolate hydroquinone having a high purity at a commercially acceptable recovery yield. This is because the reaction mixture contains various components other than p-DHP including by-products derived from these components as well as by-products derived by p-DHP.
For convenience the following abbreviations are used in the following description:
p-DHP=p-diisopropylbenzene dihydroperoxide PA0 p-DIPB=p-diisopropylbenzene PA0 p-MHP=p-diisopropylbenzene monohydroperoxide PA0 p-HHP=p-2-hydroxy-2-propyl-.alpha.,.alpha.-dimethylbenzylhydroperoxide
Various attempts have been made to recover hydroquinone having a high purity at a good recovery yield. However, there have been few methods proposed that are convenient to operate and achieve the desired quality of the purified hydroquinone as well as the yield of the purified hydroquinone based on p-DHP. Thus, prior to the present invention there are no methods for recovering hydroquinone which satisfy all the above-mentioned requirements.